Georgia - Samtskhe-Javakheti Roads 2007-2012

The evaluation uses three methodologies to rigorously evaluate the causal impact of the program on outcomes. The first is a difference-in-difference methodology, whereby the project roads are matched to a set of similar comparison roads where no intervention has taken place. These comparison roads are chosen from a number of potential candidates using a propensity score matching technique. The difference-in-difference analysis thus compares traffic counts as well as socioeconomic outcomes for residents of communities located near the project roads to those of residents of communities located near the comparison roads. Secondly, the evaluation incorporates a continuous treatment approach. Project impact is modeled in a dose-response framework, so that communities nearer the project roads are assumed to experience greater impacts than those more distant. Finally, the evaluation estimates a matched difference-indifference model, using propensity score matching to improve the comparability between the treatment and comparison groups. Combining these three approaches allows for results from each to be compared in order to ensure a robust set of findings that is not dependent on the assumptions of one particular modeling approach.